The new technique of Fourier-transformed infrared photoacoustic spectroscopy developed on this project will be developed to explore its application to in-situ testing of biological materials. Three new techniques for fluorescent - lifetime measurement of extrinsic probes in the 0.02-1.00 nsec range will be developed with a view to examining the rapid relaxation of the membrane solvent-cage about the excited electronic state of the extrinsic probe. Piezoelectric detection will be used to obtain a quantitative measure of the relative probabilities of radiationless transitions for extrinsic probes in different lipid environments. Work on the interaction of probes and simple retinoids with cell-surface proteins will continue. Extrinsic probes containing chromophores with large S sub l --- S sub o dipole moment changes will be studied in an effort to show the potential of the edge-excitation red-shift as a simple but sensitive measure of the relaxation ability of the solvent-cage formed by the membrane about the probe.